Members of Cablevision’s founding family are suing the company that took over the cable operator in 2016, accusing it of violating a merger agreement by laying off workers at television news stations serving the New York metropolitan area.

Cablevision founder and former chief executive Charles F. Dolan, his wife Helen A. Dolan, sons James and Patrick Dolan and News 12 Networks anchor Colleen McVey asked a Delaware state court to block Altice from laying off News 12 employees “other than in the ordinary course of business” for obvious cause.

The lawsuit is targeting
Altice USA Inc.,
ATUS -1.19%
which was spun off from its corporate parent earlier this year, and Altice Europe NV, which comprises the company’s international holdings.

In the complaint filed Tuesday, the Dolans and Ms. McVey indicate that Altice “recently informed the Dolans” about plans to lay off a number of News 12 employees, including Ms. McVey. Last year, the Dolan family says in its complaint, Altice laid off about 70 News 12 employees.

“Our ratings and digital growth show that viewers are responding positively to our efforts,” she said in an emailed statement.

Asked if the company intended to lay off employees as indicated by the Dolan family, Ms. Anselmo wrote back: “We will be responding to the allegations in due course now that we are in litigation.”

News 12, which the family describes in court documents as “the crown jewel” of Cablevision’s assets, was founded in 1986 as a 24-hour regional cable news service.

“It was a project conceived by my father, Charles,” said Patrick Dolan in a telephone conversation Tuesday. “We consider it a public trust.”

During deal talks with Altice, according to the complaint, News 12 became the sticking point, with the Dolan family asking at one point that News 12 be spun off “and not controlled by Altice.”

“We had a lot of concerns about News 12 given Altice’s reputation about cost cutting,” said Patrick Dolan, who was president of News 12 when the merger was negotiated and remains senior network adviser. Mr. Dolan is also the owner of Newsday, Long Island’s Pulitzer Prize-winning newspaper.

Altice, the Dolans say, agreed to maintain News 12 at about 462 employees through at least the end of 2020, assuming certain revenue levels.